Live Expressions in the Console

Pin a Live Expression to the top of your Console when you want to monitor its value in
real-time.

Click Create Live Expression.
The Live Expression UI opens.

Figure 1. The Live Expression UI

Type the expression that you want to monitor.

Figure 2. Typing Date.now() into the Live Expression UI

Click outside of the Live Expression UI to save your expression.

Figure 3. A saved Live Expression

Live Expression values update every 250 milliseconds.

Highlight DOM nodes during Eager Evaluation

Type an expression that evaluates to a DOM node in the Console and Eager Evaluation
now highlights that node in the viewport.

Note:The highlighted node only updates when you type. It does not update on an interval.
For example, if you type document.activeElement, which tracks the element in focus, and then
tab through the page, DevTools will still be highlighting the node that was active when you originally
typed out the expression.Figure 4. Since the current expression evaluates to a node, that node is highlighted
in the viewport

Here are some expressions you may find useful:

document.activeElement for highlighting the node that currently has focus.

document.querySelector(s) for highlighting an arbitrary node, where s is a CSS selector.
This is equivalent to hovering over a node in the DOM Tree.

$0 for highlighting whatever node is currently
selected in the DOM Tree.

$0.parentElement to highlight the parent of the currently-selected node.

Performance panel optimizations

When profiling a large page, the Performance panel previously took tens of seconds to process
and visualize the data. Clicking on a event to learn more about it in the Summary tab also
sometimes took multiple seconds to load. Processing and visualizing is faster in Chrome 70.

Figure 5. Processing and loading Performance data

More reliable debugging

Chrome 70 fixes some bugs that were causing breakpoints to disappear or not get
triggered.

It also fixes bugs related to sourcemaps. Some TypeScript users would instruct
DevTools to blackbox a certain TypeScript file while stepping through code, and instead DevTools
would blackbox the entire bundled JavaScript file.
These fixes also address an issue that was causing the Sources panel to generally run slowly.

Enable network throttling from the Command Menu

You can now set network throttling to fast 3G or slow 3G from the Command Menu.

Want to measure how long it takes real users to complete critical journeys on your pages?
Consider instrumenting your code with the User Timing API.

For example, suppose you wanted to measure how long a user spends on your homepage before
clicking your call-to-action (CTA) button. First, you would mark the
beginning of the journey in an event handler associated to a page load event, such as
DOMContentLoaded:

This also comes in handy when debugging or optimizing code. For example, if you want to optimize
a certain phase of your lifecycle, call window.performance.mark() at the beginning and end of your
lifecycle function. React does this in development mode.

Feedback

To discuss the new features and changes in this post, or anything else related to DevTools:

Consider Canary

If you're on Mac or Windows, consider using Chrome Canary as your default
development browser. Canary gives you access to the latest DevTools features.

Note: Canary is released as soon as its built, without testing. This means that Canary
breaks about once-a-month. It's usually fixed within a day. You can go back to using Chrome
Stable while Canary is broken.

Discover other DevTools features

Below is a list of everything that's been covered in the What's New In DevTools series.